When I last looked into it - back in Sydney - the only suggestions involved things like spraying the concentrated wee of predatory animals. The squirrels were supposed to detect the smell, fear for their lives, and flee. I never found out how you obtained such a thing.

The cages I built were very simple affairs. Three or four stakes in the ground, wrapped in sturdy chicken wire, capped with some more chicken wire. You just have to allow yourself access to the plants.

I think, though, that you're only in trouble if the squirrels actually discover the fruit. Wait and see.